The present invention relates to a plastic welding apparatus, and more particularly, to a laser welding apparatus having a pressing device with a window which allows a laser beam to pass through and weld two materials together while the pressing device holds the material together.
Plastic containers are widely used for the packaging of food and for a wide variety of other items wherein a pouch is formed by folding a flat piece of plastic membrane into a general form of a bag, and one edge of the membrane is sealed to another edge by the use of heat. In another application, a semi-rigid plastic container is filled with a product and a plastic lid is bonded to the container by the application of heat. The required heat can be provided by an electric hot plate which partially melts portions of the lid and container so the lid fuses to the container. When the hot plate is mounted adjacent to the lid, heat must transfer through the lid to the junction between the lid and the container in order to melt portions of the container which fuses to the lid. As a result the operation is relatively slow.
Another method of bonding involves the use of laminated plastic lids each having a layer of metal foil. An oscillating magnetic field induces an electrical current into the metal foil to develop heat which melts portions of the lid and container and fuses the lid to a lip of the container. An induction coil having an electrical current directs the oscillating magnetic field to an area adjacent to the junction of the lid and container lip. This operation will not work with an all-plastic material. Either the laminated lid material or the material in the container must include a layer of metal material so the magnetic field can induce an electrical current in the metal material for heating the adjacent layers of plastic.